Electrostatics is concerned with the field and potential of stationary electrical charges and electric charge distributions. Problems are this type are almost exclusively concerned with mathematics of geometries using the inverse-square law.

learn more… | top users | synonyms

0
votes
0answers
26 views

Question regarding 2 conducting spheres connected by a long fine line (electric potentional)

I'm having a bit of trouble understanding a pretty simple issue. Assuming I have 2 conducting spheres uniformly charged connected by a long fine line (as shows in the added photo) and im being asked ...
3
votes
1answer
67 views

Does it really make sense to talk about field lines?

Field lines should only provide a visual representation of a field. There is a rule for their construction: take an object subject to a field, move it by d$\mathbf{r}$ and draw the direction of the ...
1
vote
2answers
123 views

Force between two charged particles [closed]

Consider two positively charged particles, one of charge $q_0$ (particle 0) fixed at the origin, and another of charge $q_1$ (particle 1) fixed on the y-axis at $(0,d_1,0)$. What is the net force ...
2
votes
3answers
413 views

Force on a point charge q inside a cavity in an uncharged conductor

This is problem 2.40 from Introduction to Electrodynamics by D. J. Griffiths: A point charge $q$ is inside a cavity (not necessarily spherical or anything similarly regular) in an uncharged ...
1
vote
1answer
58 views

Help understanding the solution to a problem regarding kinetic energy of a group of point charges

The problem provided by my professor goes as follows: "Now consider a situation in which all charges are equal to q and they simultaneously become "unglued". What speed will each charge have when a ...
0
votes
2answers
90 views

Why does holding an electrical switch in between on and off states cause sparks?

If air is a bad conductor, then why do sparks develop when an electrical switch is held in between on and off states? Why are sparks generated when cables carrying heavy electric current are brought ...
6
votes
5answers
3k views

Why can two (or more) electric field lines never cross?

The the title is self explanatory, I guess. Why can two (or more) electric field lines never cross?
3
votes
1answer
89 views

Can Gauss' Law in differential form apply to surface charges?

I'm calculating the electric field outside a coaxial cable using only Gauss' Law in differential form. The charge density on the interior solid conducting cylinder is exactly cancelled by the surface ...
1
vote
3answers
92 views

Electrostatic and gravitational forces? [closed]

Electrostatic force between two charged particles depends on the magnitude of the charges and the distance between them. If the charges have mass $m$ and $m'$ then, what will be the total force ...
3
votes
2answers
509 views

What is charge actually? How to define it? [closed]

Is charge of something for (e.g.) an electron related to electromagnetic space if it exists due to energy, due to which it may have mass? I don't know about quantum mechanics or advanced particle ...
1
vote
1answer
70 views

Clarification of multipole expansion for a point charge

In Griffith's electrodynamic: 3.4.2 He pointed out that the monopole term is the exact potential for a single point charge. However I was under the impression that different configuration of a ...
2
votes
1answer
134 views

Electric field intensity of spherical shell (with cut out cap)

Consider a charged spherical shell of radius $R$ and surface charge density $\sigma$. Choose a point on the surface of the shell and cut a spherical cap of radius $a \ll R$. What is the electric field ...
1
vote
0answers
26 views

An EM problem of polarized sphere

Today, I'm doing an EM problem and my question is exactly the same as this site shows: http://www.physicsforums.com/showthread.php?t=133501 To reiterate my confusion, why we can't use that integral ...
0
votes
3answers
155 views

question on dipole moment of water molecule

I read a line today and don't get it: "Molecules with mirror symmetry like oxygen, nitrogen, carbon dioxide, and carbon tetrachloride have no permanent dipole moments." ...
1
vote
4answers
450 views

Total Electrical potential energy of two particle system

I recently have been studying Electro-statics and I couldn't understand properly how the potential energy of two particle system is found. Suppose you have two particles with charges $Q_1$ and ...
4
votes
1answer
66 views

Electric arc due to static discharge in a T-Shirt possible?

Yesterday, when I came home, I went to the bathroom (lights off) and i took off my T-Shirt (100% cotton) which I wore under a Shirt (50% cotton, 50% polyester). I believe to have seen a small but well ...
7
votes
6answers
2k views

Why cant Electrostatic field lines form closed loops?

My physics textbook says "Electrostatic field lines do not form closed loops. This is a consequence of the conservative nature of electric field." But I cant quite understand. Can anyone elaborate? ...
2
votes
1answer
96 views

The position of center of mass of electron cloud in an atom

I read Griffiths EM today and it says something very interesting but a little bothering to me. It states for an atom, the position of center of mass of an electron cloud lies in the center of the ...
0
votes
1answer
66 views

Energy Stored in a Capacitor with and without Dielectric

I have seen the equation $V = \frac {V_0}{K}$, but also the equation $V=\frac{1}{2}CV^2$. The values of C and V increase in the same linear ration with K (because $C=KC_0$). However, as the energy ...
1
vote
0answers
54 views

What is conductivity?

I read that if we have spin $\frac{1}{2}$-particle, where a magetic force acts on, then the force is given by a drift speed times a conductivity. This conductivity is determined to be $\frac{kT}{D}$, ...
1
vote
1answer
37 views

Proton gas density

As far as I know the lightest gas is hydrogen due to low mass of its nucleus, but what if we were to somehow strip hydrogen atoms of electrons and enclose protons in a container made of teflon (high ...
2
votes
1answer
148 views

An Electric Potential Glued to a Cube-Shaped Insulator to Replicate a Point Charge: Charge Distribution

I have been going back over this problem with a friend for the better part of a day: A potential is glued to a cube-shaped insulator so that outside of the insulator the field is the same as a point ...
1
vote
3answers
148 views

How can the potential on a cube's surface replicate the potential of a point particle?

If i have a cube (either hollow, or an insulating solid) and i want its surface have a potential such that it looks like a point particle outside of the box does that mean the exact potential on the ...
9
votes
1answer
681 views

Solve my confusion about electrons?

When a glass rod is rubbed with a silk cloth, both get charged: The silk gets positively charged and the rod gets negatively charged. My question is the following: How/why do these objects return to ...
1
vote
1answer
50 views

Gauss's law problem. ( Need someone to point me in the right direction) [closed]

What force per square meter pushes 2 infinite planes charged positively when their charge density is $0.3 \, \mu C/\mathrm{m}^2$ Second part is - using Gauss's theorem derive the equation ...
-1
votes
1answer
61 views

Attraction and repulsion of charge? [duplicate]

Why do like charges on identical bodies cause a repulsion and unlike charges cause an attraction?
3
votes
1answer
70 views

Correct formula to express the potential generated by a single layer charge distribution

Assume that the closed surface $S$ encircles a volume $V$, and that a surface charge with density $\sigma$ ("single layer") is distributed over $S$. My question regards the electrostatic potential ...
1
vote
2answers
126 views

Can effect of gravity be broken (counteracted) by electric force?

Can we make a jacket using an electronic circuit that uses electric force to cancel the effect of gravity so that we get lifted in air.
1
vote
0answers
64 views

Debye Hückel Theory valid for ions?

I am wondering about the following: Is Debye Hückel Theory only used if you look at how an external "strong" field(like a potential by a sphere that has a charge that is 1000times higher than the ...
1
vote
2answers
113 views

How does particles gain electrical charges and repel each others? (electrostatic stabilization)

When I study electrostatic stabilization, I understand that the particles have same charge and thus repel others, this is how colloid is stabilize. But how does particles gain electrical charges and ...
4
votes
2answers
125 views

Argument for symmetry of potential

Consider the following electrostatic charge configuration of a spherically symmetric, perfect conductor with total charge $Q = 2q$, where $q > 0$. A point charge $q$ is placed at the position ...
0
votes
1answer
98 views

The formula used to calculate electrical potential energy

Sorry for the ugly picture but it makes my question more understandable. The $\Delta V$ from $A$ to $B$ is calculated by$$\int_A^B E \, \mathrm{d}r$$ where $r$ is the distance between $A$ and $B$. ...
3
votes
1answer
87 views

Polarization vector and bound charge

Why is it that the bound charge is $Q_b = - \oint_S{\mathbf{P} \cdot d\mathbf{S}}$? In particular, why is there a negative sign? Hayt's book on electromagnetism describes this as the "net increase in ...
0
votes
1answer
52 views

In what ratio does the charge distribute if a charge and uncharged body touch each other?

Lets say a large charged body has $n$ elementary charges and is brought in contact with a small uncharged body. When the charge distributes, does it distribute in the ratio of number of atoms or each ...
2
votes
2answers
121 views

Absolute value in the argument of a logarithm

I am wondering how the author rationalizes the removal of absolute value bars around the quotient argument of a natural logarithm. My take on this is that the potential at point $b$ MUST be greater ...
1
vote
3answers
66 views

Why don't the leaves of an electrometer repel each other in water?

A normal electrometer filled with air will repel like it should do for electrostatic demonstration, but what if it is filled with water instead or even oil, what will happen? My guess is that the ...
0
votes
1answer
40 views

Current and Voltage of electrostatic discharge

I conducted an experiment , i put a silver foil on a a CRT TV , then i open the TV, charging the foil (acting like a capacitor plate), if i approach a grounded rod to it , it will discharge with a ...
2
votes
0answers
38 views

electrons in elecrtostatic force(please read specification given below) [duplicate]

when comb is rubbed with hair, and brought near small pieces of papers, small paper pieces gets a towards comb. Here the comb gets negatively charged and when brought near piece of paper where do ...
0
votes
1answer
33 views

Charging one thing with static electricity by using battery

How can I make one thing to get statically charged by using batteries but not friction ? For example charge a rod so it can attract shredding ?
0
votes
0answers
58 views

Resistance of a cylinder contacted by two smaller circular faces

Suppose we have a solid homogeneous cylinder with radius $a$, heigth $h$ and conductivity $\sigma$. The top and the bottom face is contacted with a smaller circular face with radius $b$. How can I ...
2
votes
1answer
66 views

Capacitor in series?

Say you have two charged capacitors in series. Zoom in on one capacitor. For this specific capacitor, the charge on the two plates will be the same in magnitude, according to my textbook. My teacher ...
2
votes
4answers
376 views

Is a capacitor in an open circuit charged?

Say I have a circuit consisting of a battery, a wire, an open switch, and a capacitor. The circuit is open since the switch is open. My book says that the capacitor will only be charged when the ...
2
votes
1answer
197 views

Why the electric potential of earth is zero?

For a localized charge distribution the potential is set to zero far away from the charge distribution (at infinity) Now, when grounding a conductor, i.e. connecting it to Earth, it is said that we ...
1
vote
1answer
95 views

Field from non-conducting plate?

For a non-conducting sheet, the electric field is given by: $$E = \frac{\sigma}{2\epsilon_0}$$ where $\sigma$ is the surface charge density. This equation holds well for a finite ...
1
vote
1answer
70 views

Electric field near surface of a conductor? [duplicate]

If the electric field on a positive charge is non-zero, then the charge accelerates in the direction of the field. The field at the surface of a conductor is perpendicular to the surface. Why ...
3
votes
2answers
204 views

Charge distribution on conductors?

You have seen that the excess charge on an isolated conductor moves entirely to the conductor’s surface. However, unless the conductor is spherical, the charge does not distribute itself uniformly. ...
1
vote
2answers
270 views

Calculating the electric potential in cylindrical coordinates from constant E-field

I am having so much trouble with this problem. I feel like I shouldn't be, but I am. A uniform electric field, $\vec{E} = E_0\hat{x}$. What is the potential, expressed using cylindrical ...
0
votes
1answer
60 views

phase difference between incident plane wave incident on a dipole and radiation fields from dipole

i have an incident plane wave and a dipole, consider that plane wave incident on dipole. at this moment what happen for dipole ? we know that after incident of plane wave on dipole, the radiation have ...
0
votes
1answer
226 views

How do you solve Laplace's equation for a parallel plate capacitor?

I would like to find the analytic solution to the problem of two plates of opposite electric potential. I have already solved this numerically as shown in the picture below. I'm also wondering what ...
2
votes
3answers
115 views

Calculating the Potential from the E-Field

I find that often times I'll be tripped up by questioning whether or not I can do something mathematically, and be unable to come up with a satisfying answer. This is, unfortunately, one of those ...